1. Field of the Invention
The present invention relates to a sheet processing device comprising measuring equipment for measuring a property of media sheets to be processed in the device, and a controller arranged to control a processing operation of the device on the basis of the measured property.
More particularly, the present invention relates to a printing device in which an image is formed on one or both sides of each media sheet.
An example of a property to be measured is the thickness of media sheets of a given type. This information may be needed for example for predicting the time when the maximum storage capacity of a sheet output stacker of the printing device will be reached and the stack of printed sheets will have to be removed. In order to predict how the height of the stack increases when sheets are processed and discharged onto the stack, it is necessary to know the thickness of the individual sheets.
In an ink jet printer, for example, the thickness information may also be needed for appropriately setting the height of the print head relative to the sheet transport path on which the sheets pass by underneath the print head.
As another example, when the printed sheets are intended for booklets, the measured sheet thickness may be used for calculating a so-called image creep that typically occurs when a booklet is formed.
Other examples of relevant media sheet properties that may be measured include the grain direction of paper sheets, the weight of the sheets, the stiffness of the sheets, humidity content of the sheets, and the like.
2. Description of the Background Art
If the type of the media sheets to be processed is known, it is frequently possible to retrieve the relevant sheet properties from a media catalogue in which the media type is listed. However, there may be cases where the media type is not known or the property information in the media catalogue is not exact or not reliable enough, for example, when the media properties depend upon varying environmental conditions such as temperature, air humidity and the like. For this reason, many printing devices have suitable measuring equipment for measuring the relevant properties of the media sheets that have been loaded into the device.
In a typical print shop, a plurality of printing devices are available, and these devices may have different features and different capabilities as far as the measurement of the media sheet properties is concerned. U.S. Application Publication No. 2012/287464 discloses a method of synchronizing media lists that are stored in different printing devices, so that the information on media sheet properties, as retrieved from a media catalogue, may be exchanged between the printing devices.